Brake assemblies particularly adapted for vehicular brakes that use a power screw that is rotated in opposite directions to correspondly move a brake member towards and away from a rotatable braking surface upon respective application and release of the brake by an operator have been known for many years.
Examples of braking assemblies utilizing such power screws are respectively disclosed in U.S. Pat. Nos. 3,765,515; 3,835,961; 3,942,827; 4,122,300; 3,976,168; 4,014,411; 4,036,330; 4,319,669; 4,355,708; and 4,406,352, the disclosures of all of which are included herein by reference.
Generally, the power screw is actuated in some manner by respective application and release of the brake by an operator and is threadingly engaged with a nut member disposed coaxially thereabout that is adapted to move the braking member in opposite brake applying and brake releasing directions in response to opposite axial movement thereof along the power screw.
The braking member generally includes a layer of frictional material that is urged against the rotatable braking surface upon application of the brake and typically becomes worn over a period of time resulting in increased clearance between the braking member and the braking surface in the brake released condition. In order to compensate for such wear, a variety of automatic slack adjusters have been developed over the years such as disclosed in the above referenced patents to maintain as best as possible a substantially constant clearance between the braking member and the braking surface in the brake released condition to minimize slack.
Automatic slack adjusters for use with power screws generally involve some means of automatically rotating the nut member an angular amount required to advance the nut member axially along the screw any clearance correcting distance required to maintain an initial desired clearance between the braking member and the braking surface in a brake released condition upon application of the brake by the operator. Understandably, such adjusters must be accurate and simple to operate and maintain. However, automatic slack adjuster must also be provided with means for preventing back-off of the nut member upon release of the brake by an operator as well as some means of preventing continued rotation of the nut member once the braking member becomes engaged with the braking surface. It is to the totality of providing an accurate and easily maintained automatic slack adjusting system coupled with means for preventing back-off of the nut member as well as preventing continued rotation thereof upon engagement between the braking member and braking surface to which this invention is addressed.